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Prevalence of Nasal Carriage of Staphylococcus aureus among Medical and Veterinary Students
Dr. Salina Akter
Roll No.: 0120/17 Registration No.: 899
Session: 2020-2021
A thesis submitted in partial fulfillment of the requirements for the degree of Master in Public Health
One Health Institute
Chattogram Veterinary and Animal Sciences University Chattogram-4225, Bangladesh
December 2022
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Authorization
I hereby declare that I am the sole author of the thesis. I also authorize the Chattogram Veterinary and Animal Sciences University (CVASU) to lend this thesis to other institutions or individuals for the purpose of scholarly research. I further authorize CVASU to reproduce the thesis by photocopying or by other means, in total or in part at the request of other institutions or other individuals for the purpose of scholarly research.
I, the undersigned, and author of this work, declare that the electronic copy of this thesis provided to the CVASU library, is an accurate copy of the print thesis submitted, within the limits of the technology available.
Dr. Salina Akter December 2022
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Prevalence of Nasal Carriage of Staphylococcus aureus among Medical and Veterinary Students
Dr. Salina Akter
Roll No.: 0120/17 Registration No.: 899
Session: 2020-2021
This is to certify that we have examined the above Master’s thesis and have found that is complete and satisfactory in all respects, and that all revisions required by the thesis examination committee have been made.
--- --- Supervisor Co-supervisor
Dr. Himel Barua Dr. Eaftekhar Ahmed Rana
Professor, Dept. of Microbiology and Assistant Professor, Dept. of Microbiology and
Veterinary Public Health Veterinary Public Health
--- Chairman of the Examination Committee
Professor Dr. Sharmin Chowdhury Director, One Health Institute
One Health Institute
Chattogram Veterinary and Animal Sciences University Chattogram-4225, Bangladesh
December 2022
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Acknowledgments
The author would like to acknowledge the Almighty for giving her life, hope, courage, strength and perseverance to carry on despite all the challenges. The author feels highly privileged to express her profound sense of gratitude and veneration to her supervisor Dr. Himel Barua, Professor, Department of Microbiology and Veterinary Public Health, for his valuable and critical suggestions, scientific acumen, perspicacious remarks, scholarly guidance, blessings and inspiration throughout the course of this study, research works and preparation of this manuscript.
The author expresses her sincere and unfathomable sense of gratitude to Dr. Sharmin Chowdhury, Director, One Health Institute for her constructive advice and encouragement at various stages of this study. The author records her gratitude to her Co-supervisor Dr. Eaftekhar Ahmed Rana, Assistant Professor, Department of Microbiology and Veterinary Public Health, CVASU for his guidance and continuous support.
With special pleasure, author acknowledges the Coordinator of Advanced Studies and Research and Committee of Advanced Studies and Research, CVASU for providing her a research grant to accomplish her research work.
Author gives sincere thanks to her family, especially her mother Minara Begum, husband Mohammed Golam Rashid who constantly support her. Very sincere thanks to the examiners for helping her to refine this work further.
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Table of Contents Page
Authorization 2
Signature Page 3
Acknowledgements 4
List of Figures 6
List of Tables 7
List of Abbreviations 9
Abstract 10
1. Introduction 1
2. Review of Literatures 3
3. Materials and Methods 19
4. Results 25
5. Discussion 41
6. Conclusions 43
7. References 44
Appendix A: questionnaire 55
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Name of figure Page
no.
Figure 1: Importance of alfa toxin in S.aureus infection 5 Figure 2: Main spread and transmission mechanism of S. aureus and impact of nasal carriage on subsequent infections
8 Figure 3: Mechanism of S. aureus in nasal colonization 9 Figure 4. Characteristic growth of staphylococci on blood agar 26 Figure 5. Colony morphology of staphylococci on mannitol salt agar 26
Figure 6. Electrophoresis on agarose gel 27
Figure 7. Result of coagulase test for S. aureus 27
Figure 8. Electrophoresis on agarose gel 28
Figure 9. Heat map for Medical students 32
Figure 10. Heat map for Veterinary students 33
Figure 11. Gel electrophoresis image of PCR product of MRSA 38
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List of Tables Page
no.
Table 1. Virulence factors of S. aureus and their function (Gnanamani et al., 2017)
4 Table 2. Primer sequences used in polymerase chain reaction (PCR) to detect staphylococci and Staphylococcus aureus
21
Table 3. Contents of PCR reaction mixture for the detection of staphylococci and Staphylococcus aureus
22 Table 4. Interpretive categories and zone diameter breakpoints (CLSI,
2020)
23 Table 5. Oligonucleotide primers used in PCR to detect mecA gene 24 Table 6. Antimicrobial susceptibility pattern of coagulase-positive
Staphylococcus aureus isolated from medical students (n=10)
29 Table 7. Antimicrobial susceptibility pattern of coagulase-negative
Staphylococcus aureus isolated from medical students (n = 29)
29 Table 8. Antimicrobial susceptibility pattern of coagulase-positive
Staphylococcus aureus isolated from veterinary students (n=6)
30 Table 9. Antimicrobial susceptibility pattern of coagulase-negative
Staphylococcus aureus isolated from veterinary students (n=21)
31 Table 10. Antimicrobial resistance profile of coagulase-positive
Staphylococcus aureus isolated from medical students
33 Table 11. Antimicrobial resistance profile of coagulase-negative
Staphylococcus aureus isolated from medical students
34 Table 12. Number and percentages of Staphylococcus aureus isolated
from medical students exhibiting resistance to various number of antimicrobial classes
35 Table 13. Antimicrobial resistance profile of coagulase-positive
Staphylococcus aureus isolated from veterinary students
36 Table 14. Antimicrobial resistance profile of coagulase-negative
Staphylococcus aureus isolated from veterinary students
36 Table 15. Number and percentages of Staphylococcus aureus isolated
from veterinary students exhibiting resistance to various number of antimicrobial classes
37
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Table 16. Prevalence of mecA gene in methicillin resistant isolates obtained from medical and veterinary students
38 Table 17: Univariable logistic regression analysis of risk factors for the
carriage of S. aureus in different veterinary and medical students.
39
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List of abbreviation Abbreviations Elaborations
% Percentage
≥ Greater than or equal to
≤ Less than or equal to
95% CI 95% confidence interval
AMR Antimicrobial resistance
BA Blood agar
CVASU Chattogram Veterinary and Animal
Sciences University
MRSA Methicillin resistant Staphylococcus
aureus
MSA Mannitol salt agar
PCR Polymerase chain reaction
IAHS Institute of applied health science
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Abstract:
Staphylococcus aureus is one of the main causes of hospital and community acquired infections.
The nose is the main ecological niche where S. aureus resides, and nasal carriage among hospital personnel is one of the important sources of staphylococci for causing nosocomial infection. The aim of the present study was to determine the nasal carriage rate of S. aureus among medical and veterinary students. A cross-sectional study was conducted on a total of 157 students (81 were medical students and 76 were veterinary students) between May and October 2022. Nasal swab from each student was collected and presumptive S. aureus was identified following conventional bacteriological methods. Isolates that were catalase-positive and coagulase-positive were taken presumptively as S. aureus. Isolates that gave negative reaction to coagulase were considered as coagulase-negative staphylococci (CoNS). The identification of S. aureus was confirmed by detecting the presence of species-specific nuc gene by polymerase chain reaction (PCR) assay. All staphylococci isolates were tested for antimicrobial susceptibility by disc diffusion method with a panel of 11 antimicrobials. Isolates displaying resistance to oxacillin and cefoxitin were further tested for the presence of mecA gene by PCR. The results of the study showed that 48.15% and 35.53% of medical and veterinary students, respectively were nasal carriage of S. aureus.
Antimicrobial resistance profiling showed that all S. aureus isolates obtained from medical and veterinary students displayed resistance to Ampicillin and Penicillin. Resistance to Ciprofloxacin was varied among medical and veterinary students. About 80% of the total S. aureus isolates from medical students showed multi-drug resistance (MDR) (i.e. resistance to ≥3 antimicrobial classes) whereas about 50% of the total S. aureus from veterinary students were MDR. Among the 39 isolates obtained from medical students, 20 (51.3 %) were methicillin resistant and the rate of methicillin resistance among veterinary students was 22.2%. Only one factor presence of
“Rhinorrhea” was found significantly associated with carriage of Staphylococcus sp. among medical and veterinary students.
Keywords: Staphylococcus aureus, MRSA, Coagulase negative staphylococci, Antimicrobial resistance.
